UNIVERSITI PUTRA MALAYSIA

PERFORMANCE AND PROPERTIES OF POLYPROPYLENE-CELLULOSE AND POLYPROPYLENE- OIL PALM EMPTY FRUIT

BUNCH BIOCOMPOSITES

MOHD KHALID

FK 2007 18

PERFORMANCE AND PROPERTIES OF POLYPROPYLENE-CELLULOSE

AND POLYPROPYLENE- OIL PALM EMPTY FRUIT BUNCH BIOCOMPOSITES

By

MOHD KHALID

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,

in Fulfilment of the Requirements for the Degree of Master of Science

January 2007

DEDICATED

TO

MY FAMILY

ii

Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment of the requirement for the degree of Master of Science

PERFORMANCE AND PROPERTIES OF POLYPROPYLENE-CELLULOSE

AND POLYPROPYLENE- OIL PALM EMPTY FRUIT BUNCH BIOCOMPOSITES

By

MOHD KHALID

January 2007 Chairman: Salmaiton Ali, PhD

Faculty: Engineering

Natural fibers such as oil palm empty fruit bunch fibers (EFBF) can be used as

environmentally friendly alternatives to conventional reinforcing fibers (e.g., glass) in

composites. The interest in natural fiber-reinforced polymer composites is growing

rapidly due to its high performance in terms of mechanical properties, significant

processing advantages, excellent chemical resistance, low cost and low density. These

advantages place natural fiber composites among the high performance composites

having economic and environmental advantages. On the other hand, lack of good

interfacial adhesion and poor resistance to moisture absorption make the use of

natural fiber-reinforced composites less attractive. In order to improve their interfacial

properties, these EFB fibers were subjected to chemical treatments, namely,

chlorination, mercerization and acetylation. Preparation of cellulose by selective

removal of non-cellulosic compounds constitutes the main objective of the chemical

treatments of EFBF to improve the performance of fiber-reinforced composites. The

objective of this study was to determine the effects of cellulose on the performance of

the cellulose-reinforced biocomposites and comparing its property with the EFBF-

iii

reinforced biocomposites. Biocomposites were prepared by blending polypropylene-

cellulose and polypropylene-EFBF at different weight ratios using a twin screw

brabender. Further, effects of two different coupling agents namely MAPP and

TMPTA on the properties of PP-cellulose and PP-EFBF biocomposite were also

studied. These coupling agent were incorporated in order to enhance the fiber matrix

adhesion. Mechanical and physical properties of both the biocomposites were

evaluated. Compared to PP-EFBF biocomposites, PP-cellulose biocomposites showed

better fiber-matrix interaction as observed from the good dispersion of fibers in the

matrix system. The tensile fracture and impact fracture surfaces of the composites

were characterized by scanning electron microscopy confirms the cellulose and PP

interface had improved interfacial bonding. Incorporation of MAPP as coupling agent

does not show significant improvement in case of PP-cellulose biocomposite.

However, it showed good results for PP-EFBF biocomposite. On the other hand

TMPTA coupled PP-cellulose biocomposite offered superior physical and mechanical

properties. The strong intermolecular cellulose-matrix bonding indicates a decrease in

the high rate of water absorption in PP-cellulose biocomposites. The dynamic

mechanical analysis (DMA) and Thermogravimetry analysis (TGA) technique were

also used to measure the viscoelastic properties and melting point of both the

biocomposite. The scanning electron microscopy photographs of fiber surface

characteristics and fracture surfaces of composites clearly indicated the extent of

fiber-matrix interface adhesion.

iv

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk ijazah Master Sains.

PRESTAI DAN SIFAT BIOKOMPOSIT SELULOSA-POLIPROPELENA DAN

SERABUT TANDAN KOSONG MINYAK KELAPA SAWIT-POLIPROPELENA

Oleh

MOHD. KHALID

Januari 2007

Pengerusi: Salmiaton Ali, PhD

Fakulti: Kejuruteraan

Serabut asli seperti serabut tandan kosong minyak kelapa sawit (EFBF) boleh

digunakan sebagai alternatif komposit yang mesra alam bagi menggantikan serabut

penguatan konvensional (contoh: kaca). Minat terhadap komposit polimer penguat-

serabut asli berkembang dengan pesatnya kerana prestasi yang tinggi dari segi sifat

mekanik, faedah pemprosesan yang penting, ketahanan kimia yang cemerlang, harga

rendah dan ketumpatan rendah. Faedah-faedah ini meletakkan serabut asli antara

komposit yang tinggi kecekapan yang mempunyai faedah dari segi alam sekitar dan

ekonomik. Dalam pada itu, kekurangan dari segi lekatan antara muka dan rintangan

terhadap serapan kelembapan menyebabkan penggunaan komposit penguat-serabut

asli kurang mendapat tarikan. Untuk memperbaiki sifat-sifat antara muka mereka,

serabut tandan kosong (EFBF) bergantung kepada rawatan kimia iaitu pengklorinan,

penggilapan dan pengasetilan. Penyediaan selulosa dengan cara pembuangan sebatian

bukan selulosa yang terpilih menjadikan objektif utama rawatan kimia EFBF untuk

memperbaiki kecekapan komposit penguat-serabut. Objektif kajian ini adalah untuk

menentukan kesan-kesan selulosa terhadap keupayaan biokomposit penguat-selulosa

v

dan membandingkan sifat tersebut dengan biokomposit penguat-EFBF. Biokomposit

disediakan dengan mengadunkan selulosa-polipropelena (PP) dan EFBF-

polipropelena pada nisbah berat yang berlainan menggunakan brabender skru

berkembar. Tambahan lagi, kesan daripada dua agen pengganding yang berbeza yang

dinamakan MAPP dan TMPTA terhadap sifat-sifat biokomposit selulosa-PP dan

EFBF-PP juga dikaji. Agen pengganding ini digabungkan untuk menambah lekatan

matrik serabut. Sifat-sifat mekanik dan fizikal untuk kedua-dua biokomposit dinilai.

Berbanding dengan biokomposit EFBF-PP, biokomposit selulosa-PP menunjukkan

saling tindak matrik-serabut yang lebih baik setelah diperhatikan dari segi serakan

serabut yang baik di dalam sistem matrik. Kepatahan tegangan dan hentaman terhadap

permukaan komposit digambarkan dengan mikroskopi elektron pengimbasan (SEM)

yang mengesahkan ikatan antara muka di antara PP dan selulosa telah diperbaiki.

Penggabungan MAPP sebagai agen pengganding tidak menunjukkan sebarang

pembaikan yang bernilai bagi kes biokomposit selulosa-PP. Walaubagaimanapun, ia

menunjukkan keputusan yang bagus pada biokomposit EFBF-PP. Dalam pada itu,

biokomposit selulosa-PP terganding TMPTA menawarkan sifat-sifat mekanik dan

fizikal yang lebih baik. Ikatan matrik-selulosa antara molekul yang kuat menunjukkan

pengurangan di dalam kadar serapan air yang tinggi pada biokomposit selulosa-PP.

Teknik analisis mekanik dinamik (DMA) dan analisis termogravimetri (TGA) juga

digunakan untuk mengukur sifat-sifat likat anjal dan takat lebur untuk kedua-dua

biokomposit. Keseluruhannya, fotograf SEM untuk ciri-ciri permukaan serabut dan

permukaan kepatahan oleh komposit dengan jelasnya menunjukkan had lekatan antara

muka matrik-serabut.

vi

ACKNOWLEDGEMENTS

A research is a Herculean task, which demands exemplary commitment and hard

work. This research has enlisted the help of numerous identities, thanking whom, is

the least I can do at the completion of the project. I am immensely and whole

heartedly grateful to all the people who contributed towards the culmination of this

endeavor and emphasize the impossibility of the same without their cooperative

efforts. First and foremost, I would like to place my profound indebtness and deep

sense of gratitude to my advisor and chairman of the supervisory committee, Dr.

Salmiaton Ali, my supervisory committees, Assoc. Prof. Dr. Luqman Chuah Abdullah

and Dr. Chantara Thevy Ratnam for their wholehearted guidance and support without

which this research would not have been possible. I also thank the Head of the

Department Assoc. Prof. Dr. Robiah Yunus for being there with us with ready ear and

immense erudition despite of her busy schedule.

I wish to express my gratitude to Mr. Zahid Abdullah, Mr. Wan Ali, and Mr. Kamrol

(MINT Staff), Mr. Joha and other staff of the chemical and environmental engineering

department for their selfless help and the pains they have taken beyond the call of

their duty in shaping this research.

Lastly with unquantifiable affection and reference I wish to express my sincere

feeling to my parents and my wife in the form of words which are rather restrictive in

expression of quantum.

vii

I certify that the Examination Committee met on 19/01/2007 to conduct the final examination of Mohd. Khalid on his Master of Science in Environmental Engineering thesis entitled “Performance and Properties of Polypropylene-Cellulose and Polypropylene- Oil Palm Empty Fruit Bunch Biocomposites ” in accordance with Universiti Pertanian Malaysia (Higher degree) Act 1980 and Universiti Pertanian Malaysia (Higher degree) Regulation 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows: Robiah Yunus, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Chairman) Thomas Choong Shean Yaw, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Tinia Idaty Mohd Ghazi, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Internal Examiner) Jaafar Sahari, PhD Associate Professor Faculty of Engineering Universiti Kebangsaan Malaysia (External Examiner) HASANAH MOHD GHAZALI, PhD Professor/ Deputy Dean School of Graduate Studies Universiti Putra Malaysia Date:

viii

This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of requirement for the degree of Master of Science. The members of Supervisory Committee are as follows: Salmiaton Ali, PhD Lecturer Faculty of Engineering Universiti Putra Malaysia (Chairman)

Luqman Chuah Abdullah, PhD Associate Professor Faculty of Engineering Universiti Putra Malaysia (Member) Chantara Thevy Ratnam, PhD Research Officer Malaysian Institute for Nuclear Technology Research (MINT) (Member)

AINI IDERIS, PhD Professor/Dean School of Graduate Studies Universiti Putra Malaysia Date:

ix

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions. MOHD KHALID

Date:

x

TABLE OF CONTENTS

Pages

DEDICATION ii ABSTRACT iii ABSTRAK v ACKNOWLEDGEMENTS vii APPROVAL viii DECLARATION x LIST OF TABLES xiv LIST OF FIGURES xv LIST OF NOTATIONS AND ABBRIVATIONS xix

CHAPTER

1 INTRODUCTION 1.1 Background 1.1

1.2 Characteristics of Thermoplastic Polymers 1.4 1.3 Malaysian Scenario 1.4

1.4 Application of Biocomposites 1.5 1.5 Problem Statement 1.6 1.6 Hypothesis 1.6 1.7 Scope of Study 1.7 1.8 Objectives 1.7 1.9 Structure of Thesis 1.8

2 LITERATURE REVIEW 2.1 Natural Fibres for Reinforcement 2.1

2.2 Properties of Natural Fibers 2.2 2.2.1 Physical Properties of Natural Fibers 2.2 2.2.2 Chemical Composition of Natural Fibers 2.5 2.2.3 Mechanical Properties of Thermoplastic-Natural Fibers Biocomposites 2.10 2.2.4 Water Absorption Characteristics Thermoplastic-Natural

Fibres biocomposites 2.11 2.3 Technicalities of Cellulose Fibers-Thermoplastic

Biocomposites. 2.12 2.3.1 Fiber Dispersion 2.14 2.3.2 Fiber-Matrix Adhesion and Interaction 2.15 2.3.3 Fiber Aspect Ratio 2.18 2.3.4 Fiber Orientation 2.21 2.3.5 Fiber Volume Fraction 2.23

xi

2.4 Surface Chemical Modifications of Natural Fibers 2.25 2.4.1 Effect of Alkali Treatment (Mercerization) on

Natural Fiber 2.25 2.4.2 Effect of Crosslinking Agents on Biocomposites 2.29 2.4.3 Other Treatment Method 2.30

2.5 Effects of Fiber Surface Modifications on Lignocellulosic Fibers 2.31

2.5.1 Stress-Strain Behaviour 2.31 2.5.2 Tensile Properties of Fibers 2.32

2.6 Processing Considerations and Techniques 2.33 2.7 Effects of Fiber Surface Modifications on Biocomposite

Properties 2.37 2.7.1 Mechanical Properties of Biocomposites 2.37 2.7.2 Thermal Properties of Biocomposites 2.40

2.7.3 Dynamic Mechanical Analysis (DMA) 2.40 2.7.4 Macro-Mechanical Properties of Biocomposites 2.42

2.8 Summary 2.42

3 METHODOLOGY 3.1 Materials 3.1

3.1.1 Empty Fruit Bunch Fiber (EFBF) 3.1 3.1.2 Thermoplastic 3.2

3.1.3 Chemical and Coupling Agents 3.2 3.2 Cellulose Preparation 3.3 3.3 Biocomposite Preparation 3.4 3.4 Biocomposite Sample Preparation 3.6

3.5 Mechanical Properties of the Biocomposite 3.7 3.5.1 Tensile Strength of Biocomposites 3.7 3.5.2 Flexural Strength of Biocomposites 3.7 3.5.3 Impact Strength of Biocomposites 3.8 3.5.4 Dynamic Mechanical Analysis (DMA) 3.10

3.6 Physical Properties 3.11 3.6.1 Hardness 3.11 3.6.2 Water Absorption 3.12 3.6.3 Melt Flow Index (MFI) 3.13

3.7 Thermal Analysis 3.14 3.7.1 Thermogravimetic Analysis (TGA) 3.14

3.8 Interfacial Morphology Analysis (SEM) 3.15

4 RESULTS AND DISCUSSIONS 4.1 Mechanical Properties 4.1

4.1.1 Tensile Strength of Biocomposites 4.2 4.1.2 Flexural Modulus of Biocomposites 4.5 4.1.3 Impact Strength of Biocomposites 4.8 4.1.4 Rockwell Hardness of Biocomposites 4.11 4.15 Correlation between Fiber Structure and

Mechanical Properties 4.13 4.2 Physical Properties 4.14

xii

4.2.1 Water Absorption of Biocomposites 4.15 4.3 Flow Property 4.18

4.3.1 Melt Flow Index (MFI) 4.18 4.4 Thermal Analysis 4.21

4.4.1 Thermogravimetry Analysis (TGA) 4.21 4.5 Dynamic Mechanical Analysis (DMA) 4.27 4.6 SEM Morphological Study 4.33

5 CONCLUSIONS AND RECOMMENDATION

5.1 Conclusions 5.1 5.2 Recommendations 5.2

REFERENCES R.1 BIODATA OF THE AUTHOR B.1 LIST OF PUBLICATIONS L.1

xiii

Table

LIST OF TABLES

Page

2.1 Morphological Properties of Oil Palm Fiber in Comparison with Hardwood and Softwood 2.3

2.2 Characteristic Values for the Density, Diameter and Mechanical Properties of Natural and Synthetic Fibers 2.4

2.3 Chemical Composition, Moisture Content and Microfibrillar Angle of Natural Fibers 2.9

2.4 Summary of Previous Studies on the Natural Fiber Composites, Different Chemical Treatments and Coupling Agents 2.43

3.1 Composition of PP-Cellulose and PP-EFBF Biocomposite 3.5

3.2 Composition of PP-Cellulose and PP-EFBF Biocomposite with Coupling Agent 3.6

4.1 Summary of DTGmax Degradation Temperature of PP-Cellulose and PP-EFBF Biocomposite 4.26

4.2 Summary of Tan δmax Peak Temperature of Biocomposites

4.33

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Figure

LIST OF FIGURES

Page

1.1 Classification of Natural Fibers Which Can be Used as Fillers and Reinforcers in Polymer

1.2

2.1 Positioning of the Cellulose Fibrils in Wood and Cotton Fibers

2.5

2.2 Schematic Diagram of Cellulose Molecule

2.6

2.3 Variation in the Strength And Stiffness of Jute Fibers with Lignin Content

2.8

2.4 Variation in the Strength And Stiffness of Jute Fibers with Lignin Content

2.31

2.5 Fiber Tensile Stress and Shear Stress Variation Along the Length

2.19

2.6 Stress–Position Profiles with Fiber Length

2.20

2.7 Deformation Pattern in the Matrix Surrounding a Fiber

2.20

2.8 Schematic Representations of the Changes in Fiber Orientation Occurring During Flow

2.22

2.9 Illustration of Four Stages of Deformation of Fibers, Matrix and Composite

2.23

2.10 Typical Relationships Between Tensile Strength and Fiber Volume Fraction for Short Fiber-Reinforced Composites

2.24

2.11 Detailed Chemical Structure of a Microfibril

2.27

2.12 Detailed structural Changes of Microfibrils During Mercerization

2.28

3.1 Raw Material Empty Fruit Bunch (EFB) and Processed Empty Fruit Bunch Fibers (EFBF) of Oil Palm

3.1

3.2 Polypropylene Pellets

3.2

3.3 Production of Cellulose from EFBF by Two Stage Chemical Treatment.

3.4

xv

3.4 Production of PP-Cellulose and PP-EFBF Biocomposites

3.5

3.5 Preparation of PP-Cellulose and PP-EFBF Biocomposites Samples

3.7

3.6 Instron Universal Testing Machine for Tensile and Flexural Testing 3.83.7 Ceast-Impact Pendulum Apparatus for Impact Testing

3.9

3.8 Perkin-Elmer DMA apparatus for dynamic mechanical analysis

3.11

3.9 Rockwell Hardness Apparatus for Hardness Measurement

3.12

3.10 Water Absorption Test for Biocomposites

3.13

3.11 Melt Flow Apparatus for MFI Measurements

3.14

3.12 Perkin-Elmer TGA apparatus for thermogravimetric analyses

3.15

4.1 Effect of Filler Loading on the Tensile Strength of PP-Biocomposites

4.2

4.2 Effect of APP o Tensile Strength o PP-Biocomposites a 30 Wt % Filler Loading

4.4

4.3 Effect of TMPTA on Tensile Strength of PP-Biocomposites at 30 Wt % Filler Loading

4.5

4.4 Effect of Filler Loading on Flexural Modulus of PP-Biocomposites

4.6

4.5 Effect of MAPP on Flexural Modulus of PP-Biocomposites at 30 Wt % Filler Loading

4.7

4.6 Effect of TMPTA on Flexural Modulus of PP-Biocomposites At 30 Wt % Filler Loading

4.8

4.7 Effect of Filler Loading on Impact Strength of PP-Biocomposites

4.9

4.8 Effect of MAPP on Impact Strength of PP-Biocomposites at 30 wt % Filler Loading

4.10

4.9 Effect of TMPTA on Impact Strength of PP-Biocomposites at 30 wt % Filler Loading

4.10

4.10 Effect of Filler loading on Hardness of PP-Biocomposites

4.11

4.11 Effect of MAPP on the Hardness of PP-Biocomposites at 30 wt % Filler Loading

4.12

4.12 Effect of TMPTA on the Hardness of PP-Biocomposites at 30 wt % Filler Loading

4.13

4.13 Effect of Filler Loading on Water Absorption of PP-Biocomposites 4.16

xvi

4.14 Effect of MAPP on Water Absorption of PP-Biocomposites at

30 Wt % Filler Loading 4.174.15 Effect of TMPTA on Water Absorption of PP-Biocomposites at

30 Wt % Filler Loading

4.18

4.16 Effect of Filler Loading on Melt Flow Index of PP-Biocomposites

4.19

4.17 Effect of MAPP on Melt Flow Index of PP Biocomposites at 30 Wt % Filler Loading

4.20

4.18 Effect of TMPTA on Melt Flow Index of PP Biocomposites at 30 Wt % Filler Loading

4.21

4.19 Thermogravimetry Analysis of PP Cellulose And EFBF

4.22

4.20 Derivative Thermogravimetry Analysis of PP Cellulose and EFBF

4.23

4.21 Thermogravimetry Curves of PP-Cellulose and PP-EFBF Biocomposites

4.24

4.22 Derivative Thermogravimetry Curves of PP-Cellulose and PP-EFBF Biocomposites

4.25

4.23 Hypothetical Model of the Thermal Degradation of Cellulose

4.25

4.24 Effect of Cellulose Loading on Storage Modulus of PP Biocomposites

4.28

4.25 Effect of Filler Loading on Loss Modulus of PP Biocomposites

4.29

4.26 Effect of Filler Loading on Tan Delta of PP Biocomposites

4.30

4.27 Effect of MAPP on Tan Delta of PP-Cellulose Biocomposites at 30 Wt % Cellulose Loading

4.32

4.28 Effect of TMPTA on Tan Delta of PP-Cellulose Biocomposites at 30 Wt % Cellulose Loading

4.33

4.29 SEM Micrograph Showing Tensile Fracture Surface of 30 Wt % PP-EFBF Biocomposite

4.34

4.30 SEM Micrograph Showing Tensile Fracture Surface of 50 Wt % PP-EFBF Biocomposite

4.35

4.31 SEM Micrograph Showing Tensile Fracture Surface of 30 Wt % PP-Cellulose Biocomposite

4.36

4.32 SEM Micrograph Showing Tensile Fracture Surface of 50 Wt % PP-Cellulose Biocomposite 4.37

xvii

4.33 SEM Micrograph Showing Impact Fracture Surface of 30 Wt %

PP-EFBF Biocomposite 4.384.34 SEM Micrograph Showing Impact Fracture Surface of 30 Wt %

PP-Cellulose Biocomposite

4.38

4.35 SEM Micrograph Showing Effect of 2 Wt % MAPP on PP-EFBF Biocomposite at 30 Wt % EFBF Loading

4.40

4.36 SEM Micrograph Showing Effect of 2 Wt % MAPP on PP-Cellulose Biocomposite at 30 Wt % Cellulose Loading

4.40

4.37 SEM Micrograph Showing Effect of 2 Wt % TMPTA on PP-EFBF Biocomposite at 30 Wt % EFBF Loading

4.41

4.38 SEM Micrograph Showing Effect of 2 % TMPTA on PP-Cellulose Biocomposite at 30 Wt % Cellulose Loading

4.42

4.39 SEM Micrograph Showing Effect of 7 Wt % MAPP on PP-EFBF Biocomposite at 30 Wt % EFBF Loading

4.43

4.40 SEM Micrograph Showing Effect of 7 Wt % MAPP on PP-Cellulose Biocomposite at 30 Wt % Cellulose Loading

4.44

4.41 SEM Micrograph Showing Effect Of 7 Wt % TMPTA on PP-EFBF Biocomposite at 30 Wt % EFBF Loading

4.44

4.42 SEM Micrograph Showing Effect of 7 Wt % TMPTA on PP-Cellulose Biocomposite at 30 Wt % Cellulose Loading 4.45

xviii

ABBREVIATIONS

∆Hf Heat of Fusion

CrR Crystallinity Ratio

d Diameter

E* Storage Modulus

E’ Loss Modulus (E")

fr Hermans factor

l Fiber Length

lc Critical Length

tan δ Mechanical Damping

Tc Crystallization Temperature

Tg Glass Transition Temperature

Vc Critical Fiber Volume Fraction

Xc Crystallinity

α Melting Temperature

β Glass-Rubbery Transition

σ Tensile Strength

σ*f Fiber Tensile Strength

σfu Fiber Ultimate Strength in Tension

τy Interfacial Shear Stress

ASTM American Society for Testing and Materials

xix

BC Bacterial Cellulose

CPO Crude Palm Oil

DMA Dynamic Mechanical Analysis

DP Degree of Polymerization

DTG Degradation Temperature

EFBF Empty Fruit Bunch Fiber

EHMA Ethyl α-HydroxyMethylAcrylate FFB Fresh Fruit Bunch

HDPE High-density polyethylene

ION Ionomer-Modified Polyethylene

ISS Interfacial Shear Strength

LDPE Low-density polyethylene

LWMPP Low Molecular Weight Polypropylenes

MAPP Maleic Anhydride Modified Polypropylene

MFI Melt Flow Index

MMA Methyl Methacrylate

MPOB Malaysian Palm Oil Board

OPF Oil Palm Fronds

POME Palm Oil Mill Effluent

PP Polypropylene

RGP Refiner Ground Pulp

RH Relative Humidity

SEM Scanning Electron Microscope

TG Thermogravimetric

TGA Thermogravimetic Analysis

xx

xxi

TMPTA Trimethylolpropane Triacrylate

WPC Wood-Polymer Composites

CHAPTER 1

INTRODUCTION

1.1 Background

Over the last decade, a rapid growth occurred in the consumption of the plastic

products in various fields. However, due to diminution and escalating price of

petroleum based products, the shortage of landfill space, concern over emission

during incineration and entrapment by ingestion of packaging plastic by fish, fowl and

animals has spurred efforts to explore and develop better alternatives that are

compatible with the environment and independent of fossil fuel. More down-to-earth,

however, is the fact that our society has become very energy conscious. This also has

increased the demand for lightweight yet strong and stiff structures in all walks of life.

Composites, especially polymers reinforced with natural fibers have received growing

interest, both from the academic world and from various industries. There is a wide

variety of different natural fibers which can be applied as reinforcers or fillers. An

illustration with a classification of the various fibers is presented in Figure 1.1. All

these natural fibers consist of long cells with relatively thick cell walls which make

them stiff and strong. The chemical composition as well as the structure of plant

fibers is fairly complicated. Plant fibers are composite material designed by nature.

The fibers are basically a rigid, crystalline cellulose microfibril reinforced amorphous

lignin and/or hemicelluloses matrix. Therefore, cellulose makes the principal

component of plant fiber where it provides the main structural feature. These fibers

sometimes are referred as lignocellulosic fibers due to the presence of lignin and

hemicellulose. The most important of the natural fibers used in composite materials

are flax, hemp, jute, kenaf sisal and empty fruit bunch fibers, due to their good

properties and availability.

Figure 1.1 Classification of natural fibers which can be used as fillers and reinforcers in Polymer (Mohanty et al., 2002). Generally, four main reasons are mentioned which make the application of natural

fibers attractive: (1) their specific properties, (2) their price, (3) their health

advantages and (4) their recyclability. Natural fibers based on cellulose have a

relatively low density, and are relatively stiff and strong. Therefore their specific

properties are rather high, and actually comparable to those of conventional

reinforcing fibers. Though, the environmental driving force has never been as

important as it is in today’s scenario. Natural fiber reinforced composites are

1.2

originally aimed at the replacement of glass fiber and other inorganic fiber reinforced

composites. A specific advantage of fiber composites over glass fiber composites,

however, is the fact that they can be burned (thermal recycling) without leaving large

amounts of slag. On the whole, the use of natural fibers has a definite ‘green image’.

For the automotive industry, for instance, this has been a serious driving force for the

development of natural fiber reinforced materials and it has also induced companies

like DaimlerChrysler AG, Mercedes and Ford to try and develop high performance

materials on the basis of renewable resources (Mapelstone, 1999; Broge, 2000).

Considering all the above advantages natural fiber-reinforced thermoplastic

composites eventually form a new class of materials. This seems to have a good

potential in the future as a substitute for wood and petroleum based material in

numerous applications. But, in reality lack of good interfacial adhesion and poor

resistance to moisture absorption makes the use of natural fiber-reinforced composites

slightly tedious. To overcome these problems various fiber surface treatments like

mercerization, isocyanate treatment, acrylation, latex coating, permanganate

treatment, acetylation, silane treatment and peroxide treatment have been set up which

may result in improving composite properties. Reinforcing fibers are normally given

surface treatments to improve their compatibility with the polymer matrix as

interfaces play an important role in the physical and mechanical properties of

composites. Research on a cost effective modification of natural fibers is necessary

since the main attraction for today’s market of biocomposites is the competitive cost

of natural fiber.

1.3